1. Field of the Invention
The present invention relates to a vehicle wheel which reduces a noise emission accompanying an air column resonance (cavernous resonance) inside a tire air chamber.
2. Description of Related Art
In general, it is known that an air column resonance generated in an air chamber of a tire (hereinafter, referred to as tire air chamber) causes a road noise of a vehicle. The air column resonance is a phenomenon which generates a resonant sound in such a manner that random vibrations transmitted from a road surface to the tire vibrate air in the tire air chamber, and consequently a resonant phenomenon is generated at around an air column resonance frequency of the tire air chamber.
Conventionally, a vehicle wheel described in Japanese Patent No. 3992566 has been known as a vehicle wheel which reduces a noise emission accompanying the air column resonance. The vehicle wheel includes a plurality of additional air chambers along a circumferential direction of a rim. In more detail, in the vehicle wheel, a circular space portion formed between a circular vertical wall, which is vertically disposed in a well portion and extending in the circumferential direction of the rim, and a rising side wall of the well portion toward a bead seat portion is covered with a cap member. The circular space portion zoned by the cap member, the well portion and the vertical wall is partitioned by a plurality of separators disposed at a predetermined interval in the wheel circumferential direction to form each additional air chamber. In addition, the tire air chamber and each additional air chamber are communicated with each other through a communication hole formed in the cap member. In the vehicle wheel described above, the communication hole and the additional air chamber constitute a Helmholtz resonator and the air column resonance sound inside the tire air chamber can be reduced by the resonator.
However, a structure of the conventional vehicle wheel was not a practical structure. That is, it was required to accurately joint a plurality of separators and the cap member to the vehicle wheel having a vertical wall rising from the well portion by welding, bonding, fitting or fastening, while keeping airtightness. Accordingly, the vehicle wheel was not suitable for a mass production in view of securing the airtightness, and an increase in the manufacturing workload or the manufacturing cost.
Hence, in view of solving the above-identified problems, inventors of the present invention proposed a vehicle wheel which can be manufactured by only fitting an additional air chamber member having an additional air chamber in a space between a first vertical wall surface and a second vertical wall surface formed in a well portion (JP 2007-125139, filed on May 10, 2007, not laid-open yet).
In the vehicle wheel, the additional air chamber member has the edge portions extending to the first vertical wall surface and the second vertical wall surface and the edge portions are locked to locking portions formed on the first vertical wall surface and the second vertical wall surface, respectively. The additional air chamber member can be fitted in a space between the first vertical wall surface and the second vertical wall surface only by locking the edge portions to the respective locking portions of the first vertical wall surface and the second vertical wall surface, by utilizing elasticity of the edge portions.
According to the vehicle wheel, a mass productivity of the vehicle wheel can be improved, as the manufacturing workload and manufacturing cost can be reduced in comparison with a conventional vehicle wheel.
Meanwhile, in the vehicle wheel, a communication hole disposed in the additional air chamber member was formed to be opened in the wheel width direction. In addition, a discharge port of an air valve for supplying air to a tire air chamber was also formed directed to the wheel width direction. Therefore, when a tire pressure is adjusted, if a water is accumulated, for example, in an air compressor, or tire repairing agent is used, there is a possibility that the water or the agent may enter the additional air chamber through the communication hole, and thereby, a volume of the additional air chamber may be changed due to the entering of, for example, the water. Hence, it is required that these substances such as water are prevented from entering the additional air chamber.
It is, therefore, an object of the present invention to solve the foregoing problems and hence to provide a vehicle wheel which can prevent, for example, water from entering an additional air chamber and can preferably reduce an air column resonance sound.